1. Field of the Invention
The invention relates generally to radar apparatus. More particularly, the invention relates to efficient calibration of radar apparatus that may provide for, but is not necessarily limited to, accurate angle-of-arrival calibration of a phased array radar apparatus.
2. Description of the Related Art
Radar apparatus are commonly used in commercial and military settings for purposes of identifying and tracking a particular radar target within a particular geometric radar field of interest. In order to provide for accurate identification and tracking of such a radar target, radar apparatus typically require calibration. For example, accurate angle-of-arrival measurement within a radar apparatus often requires calibration of a radar antenna within the radar apparatus.
Such calibration of a radar antenna is often accomplished by measurement of radar antenna performance in a radar antenna test range, such as but not limited to an anechoic chamber or a near field test range, and subsequent construction of a look-up table that relates radar antenna output signal voltages to incoming radar signals angle-of-arrival. In addition to such initial radar antenna calibration, recalibration of a radar antenna or radar apparatus is also typically desirable under circumstances of radar antenna or radar apparatus malfunction or repair.
Calibration of radar apparatus may be effected subsequent to installation of the radar apparatus. Such post installation calibration of radar apparatus is often essential for assuring accuracy of such installed radar apparatus.
While post installation calibration of radar apparatus is thus a common and operative procedure for radar apparatus calibration, nonetheless in certain military settings, such as hostile environment settings, field calibration of radar apparatus may present some difficulties or may not otherwise be practical.
Thus, desirable within radar apparatus are methods that provide for radar apparatus calibration in other than field environments so as to assure efficient operation of the radar apparatus in field environments. Calibration methods are also desired, as well, that avoid the need for labor and time intensive measurements in a radar antenna test range, such as an anechoic chamber or a near-field test range.